The overall goal of the projects outlined below is to characterize the functional requirement of the muscle-enriched transcription factor, M-CAT binding factor (MCBF) for auxiliary proteins, other DNA-bound transcription factors and transcriptional intermediary factors, and particularly to investigate the basis of its differing requirements in cardiac and skeletal myocytes. 1. To investigate the requirement of MCBF for transcriptional intermediary factors. 2. To examine the means by which MCBF interacts with other promoter- bound transcription factors to produce a synergistic activation of transcription. 3. To determine the basis for the additional requirement for distal promoter sequences (the 'cardiac element"), and associated transcription factor(s), for activation of the cTNT promoter in myocardial cells versus embryonic skeletal muscle cell.